Centrifugal fan

ABSTRACT

A centrifugal fan is provided. The centrifugal fan includes a shaft and a plurality of blades. The blades is disposed on the shaft and surround the shaft, and outer edges of the blades define a circle. The circle includes an outer region adjacent to a boundary of the circle, each of the blades includes a first contour line and a second contour line within the outer region, and the neighboring blades include an air channel therebetween, which expands toward the outer edges of the blades according to an interval expanding ratio.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial No. 109118897, filed on Jun. 5, 2020. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of the specification.

BACKGROUND OF THE INVENTION Field of the Invention

The disclosure relates to a fan, and in particular, to a centrifugal fan for an electronic device.

Description of the Related Art

A centrifugal fan is formed by a plurality of blades arranged in a ring shape. When the fan runs, airflow flows in a centrifugal direction through channels between blades, and then flows into a fan frame channel of the fan.

Generally, performance of the fan is adjusted by changing a design of a blade contour line and a quantity of blades. However, in the conventional art, when the blade contour line of the fan is designed, an airflow occurred between the blades is not taken into consideration, and it is easy to generate eddy currents. As a result, the performance of the fan is reduced, and a large amount of airflow noise are generated.

BRIEF SUMMARY OF THE INVENTION

The disclosure provides a centrifugal fan. The centrifugal fan includes a shaft and a plurality of blades. The blades are disposed on the shaft and surround the shaft, and outer edges of the blades define a circle. The circle includes an outer region adjacent to a boundary of the circle, each of the blades includes a first contour line and a second contour line within the outer region, and the neighboring blades include an air channel therebetween, which expands toward the outer edges of the blades according to an interval expanding ratio.

Through the centrifugal fan provided in the disclosure, the air channel of the centrifugal fan gradually expands in a direction away from the shaft according to the interval expanding ratio, thereby improving heat dissipation efficiency by the airflow occurred in the air channel to enhance the performance of the fan and reduce airflow noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top view of an embodiment of a centrifugal fan according to the disclosure;

FIG. 2 is used for describing a definition of an interval expanding ratio;

FIG. 3A to FIG. 3D show a design process of blades in the disclosure based on a specified first contour line and a fixed interval expanding ratio;

FIG. 4 is a schematic top view of another embodiment of a centrifugal fan according to the disclosure; and

FIG. 5 is a schematic top view of another embodiment of a centrifugal fan according to the disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

More detailed descriptions of the specific embodiments of the disclosure are provided below with reference to the accompanying drawings. The features and advantages of the disclosure are described more clearly according to the following description and claims. It is to be noted that all of the drawings use very simplified forms and imprecise proportions, only being used for assisting in conveniently and clearly explaining the objective of the embodiments of the disclosure.

FIG. 1 is a schematic top view of an embodiment of a centrifugal fan according to the disclosure. The centrifugal fan 10 is applicable to an electronic device such as a notebook computer, a desktop computer, or a mainboard, to improve heat dissipation efficiency of the electronic device.

As shown in the figure, the centrifugal fan 10 includes a shaft 12 and a plurality of blades 14. The shaft 12 is connected to a driving motor. The blades 14 are disposed on the shaft 12 and surround the shaft 12, and air channels 16 of the blades 14 extend in a direction away from the shaft 12 according to an interval expanding ratio.

As shown in the figure, in an embodiment, the blade 14 is defined by a first contour line 14 a and a second contour line 14 b. The first contour line 14 a is located on a pressurized surface of the blade 14, and the second contour line 14 b is located on a rear surface of the blade 14. The first contour line 14 a and the second contour line 14 b are both in a straight contour line.

In an embodiment, according to actual requirements, the first contour line 14 a and the second contour line 14 b are in a curved-contour line. Besides, in an embodiment, a quantity of blades 14 is greater than 30, to generate sufficient airflow and provide sufficient heat dissipation efficiency. In an embodiment, to avoid affecting the airflow caused by severe changes in the air channel, an interval expanding ratio of the air channel 16 is less than 25%.

A thickness of the blade and a width of the air channel are considering limitations, that is, a thin blade affects the strength, and an extremely narrow air channel affects the airflow. In an embodiment, a thickness of the blade 14 is limited to an outer region 10 a of the centrifugal fan 10.

A circle C1 is defined by outer edges of the blades 14, and the outer region 10 a is a part of the circle C1 extending outward from 70% of the radius relative to the center. In addition, to effectively improve the airflow, in an embodiment, in the outer region 10 a, a ratio of a difference between a maximum thickness and a minimum thickness of the blade 14 and the maximum thickness of the blade 14 is greater than 30%.

Referring to FIG. 2. FIG. 2 is used for describing a definition of an interval expanding ratio. For ease of description, two neighboring blades of the centrifugal fan 10 in the disclosure are represented by using a first blade 142 and a second blade 144 below.

In an embodiment, shapes of the first blade 142 and the second blade 144 are substantially the same. The first blade 142 is defined by a first contour line 142 a and a second contour line 142 b. The first contour line 142 a is located on a pressurized surface of the first blade 142, and the second contour line 142 b is located on a rear surface of the first blade 142. The second blade 144 is defined by a third contour line 144 a and a fourth contour line 144 b. An air channel 16 is formed between the first contour line 142 a of the first blade 142 and the fourth contour line 144 b of the second blade 144, and an interval between the blades are defined.

The first contour line 142 a of the first blade 142 is set as a basic contour line, and a plurality of nodes P₁, P₂, . . . , P_(n−1), and P_(n) is set on the first contour line 142 a of the first blade 142 from the shaft 12 toward a direction away from the shaft 12.

Next, a point Q₁ closest to the node P₁ is found on the fourth contour line 144 b of the second blade 144. A distance between the node P₁ and the point Q₁ closest to the node P₁ is set as a first reference interval D1.

Similar to the foregoing manner, a point Q₂ closest to the node P₂ is found on the fourth contour line 144 b of the second blade 144. A distance between the node P₂ and the point Q₂ closest to the node P₂ is set as a second reference interval D2.

Based on this, an interval expanding ratio DR1 from the node P₁ and the node P₂ is calculated, that is, DR1=(D2−D1)/L1×100%, where L1 is a distance between the node P₁ and the node P₂.

By analogy, an interval expanding ratio DR2 corresponding to the node P₂ and the node P₃ is calculated in the same calculation manner, that is, DR2=(D3−D2)/L2×100%, where L2 is a distance between the node P₂ and the node P₃, and a distance between the node P₃ and a point Q₃ closest to the node P₃ is set as a third reference interval D3.

The foregoing definition related to the interval expanding ratio effectively describes a variation of the air channel 16. Conversely, by using the foregoing manner, a position and a shape of the fourth contour line 144 b of the second blade 144 is further calculated backward by using the first contour line 142 a of the first blade 142 via a given interval expanding ratio, thereby generating a complete second blade 144. A specific interval expanding ratio is ensured by disposing such a second blade 144 on the shaft 12. More details are described below.

Referring to FIG. 3A to FIG. 3D. FIG. 3A to FIG. 3D are used for describing a design process of blades by using a specific first contour line and a fixed interval expanding ratio. In this embodiment, blades are designed by using the first contour line 142 a in the straight contour line and a fixed interval expanding ratio.

First, as shown in FIG. 3A, a first contour line 142 a is provided. The first contour line 142 a is a basic contour line for designing a blade. Subsequently, a fifth contour line 142 c is generated by the first contour line 142 a shifting a preset distance. In this way, a provisional first blade 142′ with an equal thickness t is generated. The translation distance affects a thickness of a final newly designed blade that is generated.

Next, as shown in FIG. 3B, an angle B between the neighboring blades is calculated according to a predicted quantity A of blades, and B=360/A. Then, the first contour line 142 a and the fifth contour line 142 c of the provisional first blade 142′ are rotated by angle B, to obtain a third contour line 144 a and a sixth contour line 144 c through duplication. A provisional second blade 144′ with an equal thickness is generated by using the third contour line 144 a and the sixth contour line 144 c.

Subsequently, as shown in FIG. 3C, n nodes P₁, P₂, P₃, P₄, . . . , P_(n−2), P_(n−1), and P_(n) are defined in sequence on the first contour line 142 a from the shaft 12 toward a direction away from the shaft 12. Lines between the nodes P₁, P₂, P₃, P₄, . . . , P_(n−2), P_(n−1), P_(n) and points closest to the nodes on the sixth contour line 144 c respectively form reference lines R₁, R₂, R₃, R₄, . . . , R_(n−2), R_(n−1), and R_(n). The reference lines R₁, R₂, R₃, R₄, . . . , R_(n−2), R_(n−1), and R_(n) are used as a basis for estimating a fourth contour line 144 b.

Next, as shown in FIG. 3D, nodes P₁′, P₂′, P₃′, P₄′, . . ., P_(n−2)′, P_(n−1)′, and P_(n)′ are defined on the reference lines R₁, R₂, R₃, R₄, . . . , R_(n−2), R_(n−1), and R_(n) according to an interval expanding ratio DR. The nodes P₁′, P₂′, P₃′, P₄′, . . . , P_(n−2)′, P_(n−1)′, and P_(n) define the fourth contour line 144 b. The fourth contour line 144 b and the third contour line 144 a define a shape of a second blade 144.

Specifically, assuming that the interval expanding ratio DR is a fixed value, an expected interval value from the node Pi of the first contour line 142 a to the sixth contour line 144 c is S₁, and a distance between the node P₁ and node P₂ is L₁.

In this way, an expected interval value S₂ corresponding to the node P₂ of the first contour line 142 a is calculated, and S₂=S₁+(DR×L1). That is, an expansion value (that is, S₂−S₁) of an air channel corresponding to two neighboring nodes (that is, the node P₁ and the node P₂) is proportional to a product of the interval expanding ratio DR and the distance L1 between the two neighboring nodes (that is, the node P₁ and the node P₂).

A position of the node P₂′ on the fourth contour line 144 b is determined on the reference line R₂ by the expected interval value S₂. A closest point to the node P₁ of the first contour line 142 a on the sixth contour line 144 c is considered as the node P₁′ located on the fourth contour line 144 b. In an embodiment, to avoid affecting the airflow caused by extremely severe changes in the air channel, the interval expanding ratio DR is less than 25%.

By analogy, positions of the nodes P₁′, P₂′, P₃′, P₄′, . . . , P_(n−2)′, and P_(n−1)′ on the fourth contour line 144 b are determined by using the n nodes P₁, P₂, P₃, P₄, . . . , P_(n−2), P_(n−1), and P_(n) of the first contour line 142 a and expected interval values S₁, S₂, S₃, S₄, . . . , S_(n−2), and S_(n−1). The outermost node P_(n)′ is defined on the circle C1 by using an extension direction defined by the node P_(n−2)′ and the P_(n−1)′.

The fourth contour line 144 b is thus constructed by using the nodes P₁′, P₂′, P₃′, P₄′, . . . , P_(n−2)′, P_(n−1)′, and P_(n)′. The fourth contour line 144 b and the third contour line 144 a define the second blade 144. A thickness of the second blade 144 is of a non-equal design, that is, the second blade 144 has a thickness variation.

FIG. 4 is a schematic top view of another embodiment of a centrifugal fan according to the disclosure. Blades of a centrifugal fan 20 in this embodiment is designed by using a process similar to the process in FIG. 3A to FIG. 3D.

However, a difference between the embodiment of FIG. 1 of the disclosure and this embodiment lies in that, a second contour line 24 b in a curved-contour line is defined by using a first contour line 24 a in the curved-contour line and a fixed interval expanding ratio, thereby generating a new blade 24 to complete the centrifugal fan 20.

FIG. 5 is a schematic top view of another embodiment of a centrifugal fan according to the disclosure. A main difference between a centrifugal fan 30 in this embodiment and the centrifugal fan 20 in the embodiment of FIG. 4 is that thicknesses of the blade 24 and blade 34 are different.

In this embodiment, in a process of designing a blade, a translation distance of a first contour line 34 a is increased (corresponding to steps of FIG. 3A) to define a second contour line 34 b, thereby designing the blade 34 with a relatively large thickness.

In the foregoing embodiments, blades are designed by using a fixed interval expanding ratio. In an embodiment, the interval expanding ratio is alternatively a variation value. Further, a specific interval expanding ratio variation principle is constructed for blade design according to design expectations of a user. In an embodiment, the interval expanding ratio is linearly changed. In an embodiment, the interval expanding ratio is non-linearly changed.

In an embodiment, the interval expanding ratio is set to gradually decrease from inside to outside, to enhance the strength of an outer edge of a blade. In another embodiment, the interval expanding ratio is set to increase then decrease from inside to outside, thus to ensure the structural strength of a joint between a blade and the shaft. The foregoing descriptions are merely some possible distribution manners of the interval expanding ratio along an extension direction of the blade. A user determines a proper interval expanding ratio by analyzing a blade structure.

Through the centrifugal fan provided in the disclosure, the air channel of the centrifugal fan gradually expands in a direction away from the shaft according to an interval expanding ratio, thereby improving heat dissipation efficiency by the airflow occurred in the air channel to enhance the performance of the fan and reduce airflow noise.

The above is merely preferred embodiments of the disclosure, and does not constitute any limitation on the disclosure. Any form of equivalent replacements or modifications to the technical means and technical content disclosed in the disclosure made by a person skilled in the art without departing from the scope of the technical means of the disclosure still fall within the content of the technical means of the disclosure and the protection scope of the disclosure. 

What is claimed is:
 1. A centrifugal fan, comprising: a shaft; and a plurality of blades, disposed on the shaft and surrounding the shaft, wherein outer edges of the blades define a circle, the circle has an outer region adjacent to a boundary of the circle, each of the blade has a first contour line and a second contour line within the outer region, and the neighboring blades form an air channel therebetween, which expands toward the outer edges of the blades according to an interval expanding ratio.
 2. The centrifugal fan according to claim 1, wherein the interval expanding ratio is less than 25%.
 3. The centrifugal fan according to claim 1, wherein a ratio of a difference between a maximum thickness and a minimum thickness of the blade to the maximum thickness of the blade is greater than 30%.
 4. The centrifugal fan according to claim 1, wherein each of the blades has a thickness variation.
 5. The centrifugal fan according to claim 1, wherein a quantity of the blades is greater than
 30. 6. The centrifugal fan according to claim 1, wherein the first contour line and the second contour line are respectively located on a pressurized surface and a rear surface of the blade.
 7. The centrifugal fan according to claim 1, wherein the interval expanding ratio is a fixed value.
 8. The centrifugal fan according to claim 1, wherein the second contour line is defined according to the first contour line and the interval expanding ratio.
 9. The centrifugal fan according to claim 1, wherein the first contour line has a plurality of nodes, and an expansion value of the air channel corresponding to two neighboring nodes is proportional to a product of the interval expanding ratio and a distance between the two neighboring nodes. 